The present invention generally relates to medical devices, and more particularly, to methods of assembling catheter tips with sensors.
Catheters are widely used in the medical arts. For example, catheters are sometimes inserted into a patient""s body during mapping and ablation procedures of the patient""s heart. Catheters used for such procedures typically comprise of electrode tips and electrode rings. Various other components may also be incorporated into these medical catheters. For example, a steering mechanism allowing the physician to control the movement of the catheter while the catheter is in a patient""s body may be incorporated into the catheter. A thermistor or a thermocouple may also be placed at the catheter tip to provide temperature data. In addition, such catheters may incorporate other sensors at the tip to assist the physician in performing these delicate procedures.
One type of sensor currently being incorporated into catheter tips is an electromagnetic sensor, which provides important information to the physician about the exact location of the catheter tip relative to the patient""s body. An electromagnetic sensor used for such purposes and commercially available is a xe2x80x9c3Dxe2x80x9d sensor, which employs an orthogonal arrangement of three sensor pairs to provide three-dimensional position coordinates of the catheter tip. Details on the structure and use of a xe2x80x9c3Dxe2x80x9d sensor are discussed in PCT publication WO 00/10456, entitled xe2x80x9cIntrabody Navigation System for Medical Applications,xe2x80x9d which is hereby expressly and fully incorporated herein by reference.
Incorporating such sensors into catheter tips during assembly can be difficult. Catheters used in, for example RF ablation and mapping procedures, tend to be very small in size, thus requiring assembly techniques that must be precise. In addition, electromagnetic sensors are highly sensitive to excess thermal energy and magnetic fields. Even short exposure to excess thermal energy and magnetic fields may cause damage to these sensors.
Thus, the assembly of distal catheter assemblies that contain electromagnetic sensors are further constrained, since certain heat generating steps, for example soldering, may potentially expose these sensors to excess heat. Further, many of the components incorporated into these devices are made from ferrous material, such as stainless steel, which can magnetically affect the sensors. Thus, a method for assembling a distal catheter assembly without damaging a magnetic and heat-sensitive component contained therein would be highly desirable.
The present inventions include distal catheter assemblies, catheters, and methods that minimize damage to sensitive components.
In accordance with a first aspect of the present inventions, a distal catheter assembly comprises a housing having a proximal mounting member and a cavity formed within the housing. By way of non-limiting example, the housing can be composed of a unibody structure comprising a cap-shaped head and a cylindrical neck, with the head forming an ablation electrode and the neck forming the proximal mounting member. Ring electrodes, e.g., mapping electrodes, can optionally be disposed around the neck in electrical isolation from the ablation electrode. If the housing forms an ablation electrode, the housing can include a channel distal to the cavity, where a thermistor can be optionally mounted therein.
The distal catheter assembly further comprises a thermally or magnetically sensitive component, such as a magnetic sensor, which is mounted within the cavity. The distal catheter assembly further comprises another component mounted on the proximal mounting member. The other component can be, e.g., a steering assembly, and if the distal housing comprises an ablation electrode, an RF lead.
The proximal mounting member extends proximally from the sensitive component, providing certain advantages. For example, if the second component is composed of a ferrous material, and/or a heat generating means, such as soldering, is used to mount the second component, the effect that magnetic field and/or heat generation has on the sensitive component will be minimized due to the displacement of the proximal mounting member from the sensitive component.
Optionally, if the proximal mounting member is hollow, it may include an open window through which the inner surface of the proximal mounting member can be accessed. For example, if the second component is soldered to the inner surface of the neck, the open window may provide a working space for the soldering iron. The open window can be formed by, e.g., providing a cutout in the neck.
Access to the cavity of the housing for mounting the sensor therein can be provided by in several ways. For example, the housing may have a proximal opening, such that the sensitive component can be inserted through it into the cavity. Typically, this proximal opening will be the same opening that is in communication with a catheter body to which the distal catheter assembly will be mounted. Alternatively, the housing may have a distal opening, such that the sensitive component can be inserted through it into the cavity. If the distal opening is relatively large, it may optionally be sealed with a plug.
In accordance with a second aspect of the present inventions, a method for assembling a distal catheter assembly comprises providing a housing having a proximal mounting member. By way of non-limiting example, the housing can form an ablation electrode, in which case, the housing can further include a channel, where a thermistor can be optionally mounted therein. The method comprises mounting a thermally sensitive component, such as a 3-D magnetic sensor, within the housing by a suitable means, e.g., potting. The method further comprises mounting another component, such as a steering assembly or RF wire, on the proximal mounting member by means of heat generation, e.g., soldering.
As previously discussed, the effect that the generation of heat has on the thermally sensitive component is minimized by the displacement of the proximal mounting member from the thermally sensitive component. Preferably, to further displace the generated heat, a heat sink is placed into thermal contact with the outer surface of the housing prior to mounting the other component to the proximal mounting member. Optionally, the proximal mounting member can be hollow, in which case, a window can be formed therein to provide access to the inner surface of the proximal mounting member when mounting the other component thereto. The presence of the window provides certain advantages as previously described herein.
The sensitive component can be inserted into the cavity of the housing using a variety of methods. For example, the sensitive component can be front-loaded through a proximal opening in the housing prior to mounting the other component to the proximal mounting member. Alternatively, the sensitive component can be back-loaded through a distal opening in the housing subsequent to mounting the other component to the proximal mounting member. In this manner, the sensitive component will not be exposed at all to the heat generated as a result of the mounting process of the other component. In this case, if the distal opening is relatively large, it can be optionally sealed with a plug.